2021 年 30 巻 1 号 p. 43-59
Nonalcoholic fatty liver disease (NAFLD) is the most frequent chronic liver disease in the world. Excess fructose and sugar intake as well as high fat diet have been shown to be major risk factors for this disease. Chicken egg (egg) is a conventional food that contains every nutrient required for the growth of the chicken embryo. Eggs contain large amounts of important proteins and fat, a very small amount of carbohydrates, and all vitamins and minerals needed for development of the chick. A high sugar, glucose or fructose diet has been shown to cause fatty liver by inducing biosynthesis of glycerol and fatty acid from glucose or fructose. We analyzed the effects of eggs on the development of fatty liver induced by a high sugar, glucose or fructose diet. Feeding an egg-only diet for 4 weeks to adult C57BL/6 female mice did not induce fatty liver. In contrast, 2 to 4 weeks feeding of a sugar-, glucose- or fructose- only diet induced overt NAFLD with a large number of vacuoles observed in hepatocytes, associated with high serum level of ALT and AST. Adding boiled eggs or raw egg yolk in water to glucoseor fructose- only diet markedly suppressed NAFLD. One week raw egg yolk-only diet reversed the NAFLD caused by one week sugar-only diet. Serum ketone bodies and cholesterol levels were greatly increased in mice fed an egg-only diet. Adding raw egg yolk to sugar or changing to egg from sugar diet increased ketone bodies and cholesterol levels.